Harmonics and IMD performance may be an important specification for many telecommunication applications such as filters and duplexers. The IMD may be caused by intrinsic non-linear behavior of an acoustic resonator. This means that a resonator excited at a certain frequency may show a response not only at the excitation frequency (i.e., the fundamental frequency of the resonator), but also at other harmonic and/or intermixing frequencies.
As used herein, harmonic contributions may influence the performance of the resonator at multiples of the fundamental frequency. In embodiments, the harmonics that occur at twice the fundamental frequency may be the greatest. Thus, although an acoustic filter may have good small-signal rejection for high frequency signals, there may be output power generated at harmonic frequencies that may exceed system specifications.
As used herein, IMD may by a specification defined for resonators that use different frequency bands for uplink (i.e., transmit band or Tx band) and downlink (i.e., receive band or Rx band). Applying a signal at the transmit port and a second signal of a different frequency at an antenna port of a device may result in the two signals intermixing in a non-linear device, which may further result in signals generated at additive and subtractive combinations of the different frequencies. These signals may result in noise at a receive port of the device.